The development of mobile communication telephones has been remarkable in recent years, and with a reduced telephone charge, release of new types of telephone and the like, the number of subscribers to telephone lines of mobile communication (hereinafter referred to as “wireless telephone line”) exceeds the number of subscribers to fixed telephone lines under the present conditions. Thus, it is common practice for a user to have both of a portable telephone using a wireless telephone line and a fixed telephone using a fixed telephone line and to use them separately as required such that communication is performed with the fixed telephone indoors and communication is performed with the portable telephone while the user is out.
Reflecting such a situation, the number of subscribers to fixed telephone lines tends to decrease at present. Assuming that the usage charge (base rate and charge for calls) of telephone lines of mobile communication, communication speed, reliability of communication and the like will be further improved in the future and become approximately equal to those in fixed telephones, it is expected that the inevitability for a user to use a fixed telephone line is reduced considerably in the near future.
Also, on the other hand, it is expected that a communication function is added to a considerable number of electronic apparatuses (for example, television sets, VCRs, various kinds of cameras and the like) in the near future and various data can be transmitted and received to and from server devices or the like, and in this case, it is contemplated that a transmission/reception means for performing communication using a wireless telephone line is added to each of the electronic apparatuses. Here, when a case is assumed where a transmission/reception means using a wireless telephone line is added to various kinds of electronic apparatuses, if different wireless telephone lines are set for respective ones of the electronic apparatuses, that is, different telephone numbers are provided for respective ones, various problems arise such as unregulated creation of telephone numbers managed by users and host stations, bloating of base rate of wireless telephone lines charged to users, and even exhaustion of telephone number resources. It is thus necessary to construct a system in which a single wireless telephone line can be shared among a plurality of electronic apparatuses.
To construct such a system, a network connection through a LAN is conceivable. A proposed method is such that, for example, a short-range wireless communication device with Bluetooth (see Nikkei Electronics Jan. 17, 2000, pp. 37-44) or the like is mounted on each electronic apparatus to build a wireless LAN, and a call originated from a telephone apparatus outside the LAN is received by a master communication device such as a portable telephone for which a wireless telephone line is exclusively set in that wireless LAN to establish communication, and in the communication established state by the master communication device, each of the other electronic apparatuses (slave communication devices) in the wireless LAN performs communication with the master communication device through the short-range wireless device, thereby performing communication with the originating telephone apparatus through the master communication device.
In this method, however, only the portable telephone serving as the master communication device directly uses the wireless telephone line, and each of the other electronic apparatuses as the slave communication devices connects only indirectly to the wireless telephone line by using the portable telephone as a relay station without using the wireless telephone line.
Thus, since the master communication device must be continuously in a communication connection state during communication between a telephone apparatus outside the LAN and a slave communication device, unnecessary power consumption occurs. In addition, when a telephone apparatus outside the LAN is, for example, a computer such as a server device, and when a large amount of data such as video information transmitted from the computer is received by an electronic apparatus (slave communication device) in the wireless LAN, the portable telephone (master communication device) as the relay station bears an excessive amount of power consumption, and a burden of processing is excessive for performance of a microprocessor of a present portable telephone.
To address this, it is contemplated that that portable telephone is equipped with a battery of large capacity or a microprocessor capable of processing a large amount of data. Such a configuration, however, impairs the portability as the portable telephone and leads to a significant increase in cost, so that this is not practical.
In addition, since this method employs the portable telephone as the master communication device, an inconvenience is caused in that the portable telephone cannot be used on the move in order to perform communication between a telephone apparatus outside the LAN and an electronic apparatus (slave communication device). Thus, actually, besides the portable telephone, a wireless telephone line is required for providing each electronic apparatus in the wireless LAN with a mobile communication function.
On the other hand, in the current wireless telephone system, since a wireless telephone line is managed by a host station including a plurality of base stations and one central control station, location registration for a base station is required to use the wireless telephone line. Here, it is assumed to use a configuration in which a plurality of communication devices in the wireless LAN register their locations with the same telephone numbers, individually, the current host station cannot deal with this. Thus, to build a wireless LAN system using a wireless telephone line, the configuration which gives consideration to the issue of location registration of each communication device must be used.
As one strategy to solve such a problem, the present applicant has already proposed “Control Delegation System for Telephone Line” (Japan Patent Application 2000-122791, Japan Patent No. 3153213). When this system is applied to a wireless LAN using a wireless telephone line, each slave communication device uses a slave ID (for example, a telephone number “090-1234-5678-01,” “090-1234-5678-02” . . . ) created on the basis of a master ID (for example, a telephone number “090-1234-5678”) of a master communication device and individually performs communication through a host stations. Thus, after control delegation is received from the master communication device, it is possible to establish the wireless telephone line without using the master communication device as a relay station.
In the system proposed earlier, however, when each slave communication device which received control delegation uses a slave ID to perform wireless telephone communication to a telephone apparatus outside the LAN, the host station needs to authenticate the correspondence relationship between the slave ID and the master ID, causing a drawback of placing a burden of processing on the host station side (communication provider side).